The Southern High Plains of Texas represents the largest contiguous cotton production area in the U.S. The 25 county area surrounding Lubbock, Texas plants between 1.0-2.0 x 106 hectares (2.4 - 4.8 x 106 acres) of cotton annually depending upon the type of government program in existence that year. This area does not represent an ideal cotton growing area due to a relatively short growing season. Both the first and last quarters of the growing season are subject to growth-limiting night temperature conditions. The middle half of the growing season is normally characterized by high daytime temperatures. The semi arid nature of the environment presents an additional growth restriction to limited rainfall (50 cm/year) and extremely large evaporative demand (250 cm/year) resulting in plant water stress. About 45% of the cotton production area receives supplemental irrigation. Yields average 422 kg/ha (377 lbs/acre) for the irrigated areas and 275 kg/ha (246 lbs/acre) for the dryland conditions. In spite of the vagaries of the environment, cotton production can be profitable especially when compared to grain production.

The purpose of this paper is to describe the developmental and physiological responses of cotton cultivars adapted to this environment to the temperature conditions prevailing during the growing season.